1. Field of the Invention
The present invention is related to a method, an apparatus, and a program for measuring the sizes of tumor regions that appear within three dimensional medical images.
2. Description of the Related Art
Conventionally, the malignancy of tumors have been evaluated by measuring the greatest diameter within a horizontal cross section (a plane that perpendicularly intersects the body axis of the tumor) of a tumor and using the measured value as an index, as disclosed in “New Guidelines to Evaluate the Response to Treatment in Solid Tumors”, P. Therasse et al., RECIST Guidelines, Journal of the National Cancer Institute, Vol. 92, No. 3, pp. 205-216, 2000.
However, in these two dimensional evaluation methods that employ the long axes (greatest diameters) and short axes of ovals that approximate the horizontal cross sections of tumors, the indices of evaluation do not appropriately reflect the three dimensional sizes of the tumors, and there are cases in which accurate evaluations cannot be performed.
On the other hand, techniques for generating three dimensional images, which are groups of great numbers of two dimensional images obtained by CT apparatuses, MRI apparatuses, ultrasound apparatuses and the like, of subjects have emerged recently. Methods for obtaining the volumes of tumors from three dimensional medical images have been proposed. Japanese Unexamined Patent Publication No. 8(1996)-299341, U.S. Patent Application Publication No. 20050129297, and Japanese Unexamined Patent Publication No. 2003-265475 disclose methods in which the volumes of tumors as indices are employed to judge the sizes of the tumors.
However, it is a fact that the lengths of the long axes and short axes of horizontal cross sections which are perpendicular to the body axes of tumors are used as indices for evaluations thereof, according to guidelines such as those disclosed in the aforementioned RECIST Guidelines, in clinical practice. There is demand for long axes and short axes that more appropriately reflect the three dimensional sizes of tumors to be provided, not only the volumes provided by the methods disclosed in the aforementioned Japanese Unexamined Patent Publications.